On Your Shore
by Le Penguin
Summary: One summer, Armin makes a strange new friend at his family's beachhouse. (Eren/Armin, mermaid AU.)
1. one if by land

Today was a wonderful day. The breeze was warm, the waves were calm, the sand — Armin wriggled his bare toes experimentally — the sand was especially sandy. He wasn't usually allowed to walk the shoreline without his parents or grandfather, but this summer, he had been granted the privilege. It made Armin feel quite grown-up. Grown-up enough, even, to steel his courage and wade out to the interesting-looking rock that was just off-shore; that was just big enough for a very grown-up seven-year-old with a backpack heavy with books and a sandwich bag full of goldfish crackers to throw to the fish.

He marveled at the view — it wasn't terribly high, certainly, but it was farther out into the waters than he'd ever been. The ocean floor dropped off into green-blue depths, and iridescent little fish glinted beneath the surface, shimmering in the afternoon sun. His heart fluttered at the sight.

He unzipped his backpack and retrieved his reference book, and lay on his stomach, settling in for a long afternoon. He tossed a handful of goldfish crackers into the waters, and eagerly flipped through the pages. Slender body with a small, pointed head, last dorsal ray not elongated, _Elops saurus_. Found inshore in bays and estuaries, frequently schooling in tidal pools, often confused with juvenile _Megalops atlanticus_. Diet consists mainly of fish and crustaceans.

_And crackers._ Armin stifled a giggle as he watched the fish swarm around the school of crackers, nibbling hesitantly before devouring them in one bite. He threw a fresh handful of crackers into the water, and rested his chin on his hands to watch the feast.

There used to be so, so many fish, and corals, and dolphins in the deep waters — his grandfather had told him stories in the summers before, as they walked the shoreline hand-in-hand. But, people fished too much, and built too much, and rode their boats too much. It hurt the ocean, and the fish and corals and dolphins couldn't live there anymore. Armin had gazed off into the quiet waters, and swore, swore with the determination that only a child could muster — he'd study hard, and go to school, and he'd be a marine biologist that would study the ocean; fix it back up so the fish and corals and dolphins could come home.

Armin squinted into the waters, shaken out of his reverie. The fish were wriggling away from the remaining crackers, and the remaining crackers were…

Unnaturally green eyes stared at him from beneath the waves. It was…a little boy, about his age, and he looked like he didn't have any clothes on. He also looked like he didn't have any legs. He had a tail, a long, shimmering green _tail_, green as his eyes and with long, pointed fins. The boy slowly rose to the surface, poking just his head above the water, up to his nose.

Armin and the boy locked eyes, staring for an agonizingly long moment. The boy's gaze flicked to the bag of crackers in Armin's hand. Armin slowly took another handful, and held them out.

"Here," Armin whispered, voice quavering only a little. "H…hold out your hand."

The boy drew his hand from the water, and held it out. His arms were covered in those shimmering green scales, too, and his fingers, oh, they were webbed like a frog's, but his five fingers looked human, and his hands looked human, and his face looked human…Armin delicately surrendered the handful of crackers to the boy, and laughed helplessly, joyfully as the boy plopped back underwater to enjoy the snack. Once he finished, he swam in a long, lazy circle before returning to the surface, resting his hands against Armin's rock. The way he moved was nothing like anything Armin had seen before, not in the movements of fish in the little tidal pools, not in the movements of dolphins on TV — he moved almost like an eel, but, well. Armin had never seen an eel that looked this pretty.

"My name's Armin," Armin said, quietly. "Do you live around here?"

The boy stared, unblinking. Armin supposed many fish couldn't blink.

"…I'm Eren," the boy said. The blink that followed was long and almost exaggerated. Ah, so he did blink. That was good; Armin would have been a little creeped out otherwise. "I live out farther. There isn't enough food to live here."

"Oh." Armin thought for a moment, then offered his sandwich bag. "Do you want more crackers?"


	2. two if by sea

Humans were weird. Humans were _so_ weird.

Armin had permitted him to examine his feet when asked (only fair, he'd said, since Eren had let him poke and prod at his fins - though that wasn't so bad, really, Armin was just curious, like he was, and his fingers _tickled_ ). Eren studied them with a critical eye. He knew they were called "feet" because he wasn't stupid and listened to what the elders told him about humans, but the rest...well. His feet-fingers were stumpy and not like his regular fingers, which were long and pretty even though they didn't have any webbing; how did he manage to get around in the water? He flexed the foot experimentally. Armin's feet-wrists connected the whole thing to his legs, up to his leg-elbows and meeting his body at his hips.

They were like arms, Eren supposed, but did you really need so many arms to survive outside the water? That was amazing, it really was. He and the rest of his kind managed fine with just two, and _they _had to deal with things like sharks, orcas, irate jellyfish…

And squid. Those damn giant squid, hoarding all their fish and forcing his village into a tiny corner of the sea, lest they be next on the menu. The elders said that it was all the humans' fault, for stealing away fish and allowing the squid to take control, but…

Having met Armin, it seemed that just couldn't be true.

The sun was setting, and Armin bid him good-bye; he asked him to come by again tomorrow, and maybe the day after that.

He was there all summer, after all.

He'd heard that, when you were about to die, you got flashbacks to the times you wanted to remember most.

Eren tried to lift himself on his arms, his tail twitching worthlessly. But he wasn't going to die here, he _wasn't_. He wasn't going to die beached on some shore, tangled in seaweed and baked in the sun. He was going to haul his battered self back into the ocean, bandage himself up, and tear after those fucking squid. They'd pay for what they did years ago, to his mother, his village.

They'd pay…they'd pay, every last one…

His mind was drifting; it sounded like there was a voice addressing him. He blinked, barely able to see; his whole body felt like it was turning to burning ash, and his lungs screamed in the dry air. Suddenly, a torrent of water was dumped over his body, soothing beyond comprehension. The seaweed tangling his limbs was being cut to shreds, his body being poked and prodded, all punctuated by more splashes of water. He tried to focus his eyes, tried to bat away the hands holding him down, keeping him from moving – he was losing the squid, he needed to _go –_

"Eren. Just hold on, we'll get you back to the lab…"

Eren's vision came into just enough focus. Armin. It'd been so long, but it was Armin, those were his eyes, and his hands, and…and he'd never understood why humans wore those "bathing suit" things but maybe if the ones that Armin was wearing now were in fashion, all tight and dark blue against his pale skin, then maybe…maybe, he could understand…

He felt himself being lifted, carried, set into some strange sling. The ground began moving beneath him, and more water was dumped on him.

Eren sighed, and let his eyes close.


	3. the snack that smiles back

Armin had dealt with a lot of badly-tempered patients in the marine lab, even in the short time he'd been in its employ. There were so many beachings in the area lately that it had caught the attention of scientists, conservationists, nosey news crews…Armin had learned to ignore the microphones that were shoved in his face, but sometimes, he dearly wished to take a page from the celebrity book of dealing with paparazzi and deck one of them with their own film equipment.

…that would spell bad publicity for the lab, though. He wished he was as good as Doctor Hanji at ruining their footage with her endless supply of Special Ocean Facts, that sent the crews blanching and retching off into their vans. (If they didn't want to learn about the ocean and, in that realm, have an exquisitely-detailed explanation of how old-time divers were found compressed into their helmets, why were they nosing around their beaches?) Armin just wanted to do his job, that's all; to save the poor creatures thrown battered and drying and dying onto the sands, and to find out what on earth was causing it to begin with.

He…had hoped, maybe, that his search would lead him to this point, somehow. Hoped, not daring to do much more. He _knew _that he hadn't imagined Eren as a child. He knew that he was lonely, then, and had an imagination as big as his curiosity, and that after his parents died and the beachhouse was sold, he would cling to any hazy memories of his time there, turning them over in his mind constantly, embellishing their ragged edges until they were no longer quite true.

But he distinctly remembered that long, graceful green tail that glinted through the waters – graceful beyond anything he'd ever seen before or since, in his studies. Armin wondered if anyone who'd drawn mermaids in classic art had ever seen one. Eren wasn't some plainly human top crammed onto a stumpy fish's tail. He was long, and lean, with scales up his sides and down his arms leading to long, fine fingers connected with webbing; scales up his neck leading to the fronds on the sides of his head, like long, pointed ears. (Armin remembered how those fronds shivered and fluffed out when Eren was excited, or angry, and – and how very _often_ they did so.) And those green eyes of his were a color that Armin couldn't ever have dreamed up.

His heart had stopped when he saw Eren, that impossible, beautiful creature from his childhood, lying bleeding and dying on the sands like some common fish.

Armin wouldn't let his first and truest friend be snatched away from him again. And that was the long and short of how he'd hauled him onto the truck and smuggled him into the lab's quarantine tanks.

Armin sidled into the tank room and locked the door behind him. Doctor Hanji didn't have a lot of people in her employ, but Armin wasn't quite ready to introduce Eren yet. He'd only told one person; an old acquaintance from grad school, a veterinarian specializing in large mammals who knew how to keep a secret and owed him a favor besides. Krista seemed only too eager to help, and Armin desperately needed an extra set of hands to care for Eren, and an extra set of brains to figure out how to do so. She'd proved an invaluable ally when they found another beached mer-creature, the day after, right around where he'd found Eren – that one was far surlier than Armin remembered even Eren being, and he happily surrendered her to Krista to be her pet project. He wanted to keep his attention solely focused on Eren, anyway.

It took three days for Eren to fully regain consciousness – regaining consciousness at all was quite a feat, considering the unresponsive lump of blood and flesh that he had come in as. On day four, Eren was still too weak to hold a conversation, or eat unassisted; he'd let Armin coax him into a shallow area of the tank and rested against him as Armin fed him fish-and-vitamin-powder-puree. He remembered him, or seemed to. That seemed very funny to Armin, that this fantastic creature, who made the fathomless and unmapped depths of the ocean his home, would remember the summers spent with a dull little human boy.

It was never pleasant to watch the poor creatures who found themselves in their lab's recovery tanks. Wounded and terrified and terribly out of place in a plain room with sterile white walls, Armin was usually only too happy to collect data for their beaching study, patch them up, and send them back on their way. But the pain of seeing Eren, a dear friend and representative of a lost and distant childhood, balled into a corner of the pool and warily eyeballing him from underneath the water…

Eren relaxed visibly when he registered that it was Armin who had come to call, and slowly swam to meet him at the pool's edge. Armin knelt there, setting the bucket he'd entered with next to him. His eyes swept over Eren, concerned and appraising at once.

"Are you feeling up to solid food today?" Armin asked, reaching into the bucket. "Fresh mackerel, from the harbor market down the road."

Eren held out a hand to receive the offering, and turned away to dip underneath the water to eat. Armin felt his heart skip – it was a habit of Eren's that he'd developed during their summer days together. Armin had always been scared to see him eat (_the mer-humanoid species subsists on a diet of fish and undersea plant life. Like many marine species, they consume their prey whole; however, the sight is made somewhat disturbing by their resemblance to humans._), so Eren had taken to eating the fish he caught out of the direct line of Armin's sight. With years of study and a doctorate under his belt, though, Armin felt less fear, and more fascination. Perhaps science had given him a taste for the strange.

Eren resurfaced, and held out his hand again. Armin smiled and handed another fish over. Hunger meant he was healing, and Armin would drive back to the market for three more buckets if Eren could keep them down. He only made his way through half, however, before he shook his head at the next fish Armin offered.

"No more?" Armin turned to tug a small plastic baggie out from the bucket. "Want some dessert?"

And at the sight of those little goldfish crackers, Eren _smiled_. Armin hadn't seen that smile in so, so many years, and oh, how Armin's heart soared to see that toothy mouth.

"You remembered," Eren rasped, softly, taking the bag between his fingers.

Armin tried to process the statement, and couldn't quite respond. How could he forget?

Eren held the bag between his hands, and rested his head against the side of the pool. He glanced up at Armin, hesitantly.

"You…only found me?" Eren asked, slowly, carefully. It was hard for him to speak, still, with his injuries. (Armin tried not to be too flattered that the first word out of Eren's mouth when he woke up was Armin's own name.)

Armin shook his head. "Just after you, I found a female around the same area. She wasn't as badly injured, but still in bad shape, so she's here as well. She said her name is Ymir, and she's being taken care of by Doctor Lenz. You met Doctor Lenz when she came in to take a blood sample yesterday."

Eren made a face. Armin tilted his head, concerned.

"You aren't fond of Doctor Lenz? She needed that blood sample to be sure you're doing better."

"No, Ymir is an asshole. You're sure there was no one else around? Another girl and two guys?"

Armin lowered his chin, apologetically. "I go out with the truck every day to check for beachings. I haven't found anyone except you two. I'm sorry, Eren."

Eren stared at the crackers in the baggie for a long moment before growling and tearing into them.

"S'okay," he mumbled around a mouthful. "They got away too, probably."

There was a knock upon the lab door, in the pattern that Armin and Krista had agreed upon to announce each other's presence. Regardless, Armin had Eren tuck himself tight against the pool wall, and dip beneath the surface to hide himself just enough while Armin rose to unlock the door.

Krista stood there, beaming, with medical supplies in hand and what appeared to be Ymir's seashell brassiere on her head.

"I made real progress with Ymir today," she whispered excitedly, darting into the room while Armin locked the door behind her.

"I see," Armin said mildly.

Krista set her supplies at the edge of the pool and sighed dreamily. Eren eyed her from the pool, one eyebrow arched high.

"I feel like I've made a real _connection_ between species, a real bond of understanding and trust—"

"Why the fuck are you wearing Ymir's bra on your head?" Eren interrupted.

Krista froze, her eyes darting to Eren. She touched her headgear, gingerly.

"…she…Ymir gave me this as, as a token of…she said it's a common gift of thanks in the mer-community…"

"Ymir's a fucking liar," Eren explained. "Make her put that thing back on before she gets her boobs gnawed off by sharks."

Krista hid her reddening face behind her hair as she stiffly stooped to root through her bag for her drawing needles. Armin kept his expression as neutral as possible. He needed Krista's help to take care of Eren (and Ymir, at that). It was not the time to dissolve into hysterics.

Thankfully, Krista was quite the professional herself – she remained as delicate as she usually was when taking blood samples, and finished drawing them as quickly as she started. She stood again to march back to the door, determined. She paused with one hand on the handle.

"I. Thank you very much for your insight, Eren. I am going to go speak to Ymir and return her gift."

With that, she slunk out the door, lingerie still crowning her head. Eren huffed, rubbing at his arm where the needle pricked it.

"That fucking idiot. Now's not the time to be pulling shit like that."

Armin sat at the pool's edge, letting his legs dangle into the water. Eren sidled up to them, hesitantly, then relaxed against him as Armin's hand settled atop his head.

"I'm glad she feels safe enough here to joke around with Doctor Lenz," Armin said. "I want you to feel the same way."

Eren's hand came up to curl around his foot. "Why wouldn't I feel safe with you," he mumbled.

Armin's heart felt like it would burst. He carded his fingers through Eren's hair, smoothing the water-stuck strands away from his face.

"You _are_ safe here," Armin said, low, for Eren as much as himself. "You can stay here as long as you need to recover. I'll keep going out daily to look for your other friends. And…"

Not another soul would know about Eren and Ymir's stay at the lab, scientific curiosity be damned. Armin had enough information on Krista's strained familial situation to be certain that she would not be tempted to go public with her data on the two. And after Eren recovered, with Armin's job being what it was, he could travel with the seasons to see Eren as much as he wanted, if…if Eren would agree to it.

Eren nosed at Armin's knee, bringing him back to reality.

"Crackers for lunch every day, too?" he asked, hopefully.

Armin smiled.

"If you're good."


End file.
